Ch. 3 & Ch. 4

Question 1

Why are entity integrity and referential integrity important in a database?

a. Referential integrity ensures that each row is uniquely identified by the primary key.
b. Referential integrity means that, if the foreign key contains a value, that value refers to an existing valid tuple (row) in another relation.
c. Entity integrity means that, if the foreign key contains a value, that value refers to an existing valid tuple (row) in another relation.
d. Entity integrity ensures that each row is uniquely identified by the primary key.

Answer 1

b. Referential integrity means that, if the foreign key contains a value, that value refers to an existing valid tuple (row) in another relation.
d. Entity integrity ensures that each row is uniquely identified by the primary key.

Question 2

A ____ key is defined as a key that is used strictly for data retrieval purposes.

a. lookup
b. foreign
c. candidate
d. secondary

Answer 2

d. secondary

Question 3

Briefly describe a candidate key:

Answer 3

A candidate key can be described as a superkey without unnecessary attributes–that is, a minimal superkey.

Question 4

Briefly explain why a data dictionary is necessary, and what should be included in a data dictionary.

Answer 4

It is important because it outlines your whole database. It allows your boss to see it and visualize what is in each table and what each attribute consists of. Data dictionary should include table name, attribute names, contents, type, format, domain, required, PK or FK, FK referenced table.

Question 5

A CUSTOMER table’s primary key is CUS_CODE. The CUSTOMER primary key column has no null entries, and all entries are unique. This is an example of ____ integrity.

a. entity
b. referential
c. complete
d. null

Answer 5

a. entity

Question 6

____ combines all rows from two tables, excluding duplicate rows.

a. INTERSECT
b. UNION
c. DIFFERENCE
d. SELECT

Answer 6

b. UNION

Question 7

____ yields only the rows that appear in both tables.

a. INTERSECT
b. UNION
c. DIFFERENCE
d. SELECT

Answer 7

a. INTERSECT

Question 8

A(n) ____ join links tables by selecting only the rows with common values in their common attribute(s).

a. equal
b. unique
c. foreign
d. natural

Answer 8

d. natural

Question 9

In an outer join, the matched pairs would be retained and any unmatched values in the other table would be left ____.

a. in another table
b. null
c. out of the results
d. with matching values from the original table

Answer 9

b. null

Question 10

A ____ contains at least all of the attribute names and characteristics for each table in the system.

a. data dictionary
b. relational schema
c. logical schema
d. join

Answer 10

a. data dictionary

Question 11

The ____ is actually a system-created database whose tables store the user/designer-created database characteristics and contents. (BTW, in MySQL that database is named “information_schema.”)

a. meta dictionary
b. schema
c. data dictionary
d. system catalog

Answer 11

d. system catalog

Question 12

In a database context, a(n) ____ indicates the use of different names to describe the same attribute.

a. entity
b. duplicate
c. synonym
d. homonym

Answer 12

c. synonym

Question 13

____ relational type is the “relational model ideal.”

a. 1:1
b. 1:M
c. M:1
d. M:N

Answer 13

b. 1:M

Question 14

Since it is used to link the tables that originally were related in a M:N relationship, the composite entity structure includes as foreign keys at least the ____ keys of the tables that are to be linked.

a. composite
b. super
c. primary
d. unique

Answer 14

c. primary

Question 15

When you define a table’s primary key, the DBMS automatically creates a(n) ____ index on the primary key column(s) you declared.

a. key
b. incomplete
c. unique
d. primary

Answer 15

c. unique

Question 16

A ____ should be a derived attribute.

a. person’s name
b. person’s age
c. person’s social security number
d. person’s phone number

Answer 16

b. person’s age

Question 17

In the ERD, cardinality is indicated using the ____ notation.

a. (max, min)
b. (min, max)
c. [min … max]
d. {min|max}

Answer 17

b. (min, max)

Question 18

Another word for existence-independent is ____.

a. weak
b. alone
c. unary
d. strong

Answer 18

d. strong

Question 19

When the PK of one entity does not contain the PK of a related entity, the relationship is ____.

a. missing
b. weak
c. strong
d. neutral

Answer 19

b. weak

Question 20

A ____ entity has a primary key that is partially or totally derived from the parent entity in the relationship.

a. strong
b. weak
c. existence-independent
d. relationship

Answer 20

b. weak

Question 21

The term “____” is used to label any condition in which one or more optional relationships exist.

a. participation
b. optionality
c. cardinality
d. connectivity

Answer 21

b. optionality

Question 22

The existence of a(n) ____ relationship indicates that the minimum cardinality is at least 1 for the mandatory entity.

a. mandatory
b. optional
c. multivalued
d. single-valued

Answer 22

a. mandatory

Question 23

The Crow’s foot symbol with two parallel lines indicates ____ cardinality.

a. (0,N)
b. (1,N)
c. (1,1)
d. (0,1)

Answer 23

c. (1,1)

Question 24

If an employee within an EMPLOYEE entity has a relationship with itself, that relationship is known as a ____ relationship.

a. self
b. self-referring
c. looping
d. recursive

Answer 24

d. recursive

Question 25

A(n) ____ entity is composed of the primary keys of each of the entities to be connected.

a. associative
b. recursive
c. unary
d. binary

Answer 25

a. associative